1. Field of the Invention
The invention relates to a corrosion inhibitor. The invention particularly relates to a corrosion inhibitor for use during the acid stimulation of an oil well.
2. Background of the Art
The production of oil and gas is often controlled by the rate at which oil and gas can be extracted from the subterranean formations containing them. No matter how much oil and gas is present, unless the oil and gas can flow to a well bore for removal at a commercially practical rate, it is has no value. One means for improving the rate at which oil and gas may be removed from a subterranean formation is the use of acidizing and fracturing treatments.
Such treatments use aqueous acidic solutions and are commonly carried out in hydrocarbon-containing subterranean formations to accomplish a number of purposes, one of which is to increase the permeability of the formation. The increase in formation permeability normally results in an increase in the recovery of hydrocarbons from the formation.
In acidizing treatments, aqueous acidic solutions are introduced into the subterranean formation under pressure so that the acidic solution flows into the pore spaces of the formation. The acidic solution reacts with acid-soluble materials contained in the formation which results in an increase in the size of the pore spaces and an increase in the permeability of the formation. Similarly, in fracture-acidizing treatments, one or more fractures are produced in the formation and the acidic solution is introduced into the fracture to etch flow channels in the fracture face. The acid also enlarges the pore spaces in the fracture face and in the formation.
The rate at which acidizing fluids react with reactive materials in the subterranean formation is a function of various factors including but not limited to acid concentration, temperature, fluid velocity and the type of reactive material encountered. Whatever the rate of reaction of the acidic solution, the solution can be introduced into the formation only a certain distance before it becomes spent. It is desirable to maintain the acidic solution in a reactive condition for as long a period of time as possible to maximize the permeability enhancement produced by the acidic solution.
The use of acids downhole is not without problems. One such problem is that the acids, in addition to increasing the permeability of a hydrocarbon bearing formation, may also cause excessive corrosion of the downhole metal equipment. Anything made of metal in contact with the acid may be subject to such excessive corrosion. It would be desirable in the art to use corrosion inhibitors to limit the corrosion of metal downhole during acid stimulation treatments of oil and gas wells.